After his first 100 days in command in Kabul, General McChrystal chose an audience of military specialists at London’s Institute for Strategic Studies as a platform for a public airing of the confidential assessment of the war he delivered to the Pentagon in late August, parts of which were leaked to news organizations. General McChrystal, 55, did not mention Mr. Biden or his advocacy of a scaled-down war effort during his London speech, and referred only obliquely to the debate within the Obama administration on whether to escalate the American commitment in Afghanistan by accepting his request for up to 40,000 more American troops on top of the 68,000 already deployed there or en route.

But he used the London session for a rebuttal of the idea of a more narrowly focused war. When a questioner asked him whether he would support scaling back the American military presence over the next 18 months by relinquishing the battle with the Taliban and focusing on tracking down Al Qaeda, sparing ground troops by hunting Qaeda extremists and their leaders with missiles from remotely piloted aircraft, he replied: “The short answer is: no.”

“You have to navigate from where you are, not from where you wish to be,” he said. “A strategy that does not leave Afghanistan in a stable position is probably a short-sighted strategy.”

In Washington on Thursday, Gen. David H. Petraeus told an audience that he had “not yet endorsed” General McChrystal’s specific request for additional troops, even though he has said he supports General McChrystal’s grim assessment of the war.

General Petraeus, the American commander who oversees the wars in Iraq and Afghanistan and works closely with General McChrystal, was sounding a careful note in public after participating in a three-hour strategy meeting with Mr. Obama and the administration’s national security team at the White House on Wednesday. For now, his aides say he does not want to get ahead of the president and the continuing deliberations.

Speaking with Brian Williams of NBC as part of a two-day conference with newsmakers at the Newseum in Washington, General Petraeus said that Wednesday’s meeting at the White House was “a very good and quite long discussion going back and looking at the goals and objectives and assumptions” underlying Mr. Obama’s Afghanistan strategy that the president announced in March.

At the Institute for Strategic Studies, General McChrystal noted that the former Taliban rulers of Afghanistan had provided sanctuary to Al Qaeda, from which it planned the Sept. 11, 2001, attacks on the United States, and he said political stability there was vital to regional security, as well as to the security of Britain, the United States and elsewhere.

Photo

Gen. Stanley A. McChrystal speaking in London on Thursday about the war in Afghanistan. He has requested more troops.Credit
Shaun Curry/Agence France-Presse — Getty Images

Advocating a “counterterrorist focus” in Afghanistan against Al Qaeda, instead of a “counterinsurgency focus” against the Taliban and Al Qaeda, he said, was a formula for what he called “Chaos-istan.” Proponents of that approach, he said, would accept an Afghanistan in which there was “a level of chaos, and just manage it from outside.”

The general’s troop request was at the heart of the White House strategy session on Wednesday led by Mr. Obama, which included Mr. Biden, Secretary of State Hillary Rodham Clinton, other cabinet secretaries, top generals, and General McChrystal, participating by videolink from London. The request has come as the worsening conflict in Afghanistan has prompted increased unease in the United States and Europe.

In an oblique acknowledgment of the tricky political terrain, General McChrystal said there had been no pressure on him from military superiors to scale down his troop request — a pattern that developed at points during the Iraq war, when American generals hesitated to call for more troops after the defense secretary, Donald H. Rumsfeld, ruled them out.

General McChrystal was named the new American and allied commander in Afghanistan this summer in succession to Gen. David D. McKiernan, who was removed after barely a year in the job, and retired, when Mr. Obama and Secretary of Defense Robert M. Gates decided they needed a fresh approach.

But direct contact between Mr. Obama and the Afghanistan commander has been rare. Aides in London said that Wednesday’s teleconference was only the second time since General McChrystal assumed his command in June that the two men had talked by videolink, a form of contact with field commanders that President George W. Bush, at the height of the Iraq war, used as often as once a week. Although he was out of Afghanistan on Wednesday, the aides said, General McChrystal was not invited to attend the White House strategy session in person.

But judging from General McChrystal’s relaxed demeanor at the session in London, any suggestion he might be headed for a showdown with the White House over war strategy — for the kind of clash that Gen. Douglas A. MacArthur had with President Truman during the Korean War — seemed far-fetched. He went out of his way to say that the White House strategy review was an essential part of developing a successful approach to the war. “I think the more deliberation and the more debate we have, the healthier that’s going to be,” he said.

In the war assessment he delivered to the Pentagon, he struck a note of urgency, saying that if the troop increases he had recommended were not in place within 12 months, the allied effort risked failure. But he told the London audience that the time being taken by current policy review in Washington was worth it. “I don’t think we have the luxury of going so fast that we make the wrong decision,” he said.

The general has used his London trip to make a renewed bid for an increase in Britain’s troop commitment in Afghanistan. With 9,000 soldiers, Britain currently has the second largest coalition contingent after the Americans. Officials at Britain’s Defense Ministry have said discussions with the Americans have included the possibility of about 2,500 additional troops in the British contingent.

John F. Burns reported from London, and Alan Cowell from Paris.

A version of this article appears in print on October 2, 2009, on Page A12 of the New York edition with the headline: Top U.S. Commander in Afghanistan Rejects Scaling Down Military Objectives. Order Reprints|Today's Paper|Subscribe